Theory
of glass shattering

In
one of the episodes of everyone's favourite comic, Tintin,
the professor demonstrates his devastating invention
- a speaker system that destroys any glass objects in
a certain vicinity. It worked due to resonance, but
what on earth is resonance anyway?

Resonance
is the state of an object when the frequency of applied
external oscillations matches exactly with its natural
frequency of vibration. Natural frequencies of vibrations
can be observed in simple examples like:

The 'ping' sound when
you tap a wineglass

The 'ooong' sound when
you blow across an empty glass/metal tube or bottle
(like in a xylophone)

Waves crashing on the
seashore

The up and down movement
of a bridge

The sounds of a guitar/piano
string when plucked

The 'hummm' from a tuning
fork

When resonance
occurs, the crests of the applied vibrations match
the natural reactions of the object, and thus there
is constructive interference - the crests become larger.
Each vibration after this adds to the crest until
something critical happens... like a bridge toppling
over (the Tacoma Narrows bridge is one hell of a good
example of this).